A broken torsion spring is not a weekend project, full stop - the spring is under enough tension to break a wrist or worse, and that doesn't change because the house is thirty-five years old instead of five. What you can do yourself on a late-80s door: check the track bolts for looseness, listen for grinding in the rollers, and test the auto-reverse by laying a 2x4 under the door before it closes. If the door reverses late or not at all, that's a safety sensor or a spring balance problem, and on a door this age it's usually the spring, not the sensor. We'd rather talk you out of climbing a ladder to touch cable or spring hardware than bill you for the trip afterward.